Database Development

Index

DB development

Identify all sources of input and decide on desired output

Database design begins with the identification of all input sources: forms, phone messages, handwritten data entry, inventory, lab reports & requests. Current forms are invaluable for identifying data. Sometimes design is only a matter of rearranging existing data and creating more meaningful formats. Other times it involves changing or augmenting data -- summarizing, analyzing and performing calculations. Identification of all output (reports, statistics, labels, etc.) to be generated is also important. Steps in the design approach are as follows:

Normalization reduces redundancy and aids analysis

Databases are developed based on an understanding of the system. A fundamental design task is making sure the DB includes all data necessary to generate desired information. System analysis may start with input (data) or output (needed reports, graphs etc.) as the focus. [Top]
Determine the number of needed tables and what information is to be stored in each. Few situations require just one table. Splitting a DB into multiple tables is called "normalization." It is done for two main reasons: it prevents unnecessary data duplication (conserves time, disk space, and possibly prevents errors); and it makes it easier to extract desired information.
Design tables, decide what fields to include, the field's data type and length.
Create table structures; and define, name, type, and set the size of fields.
Use sample data and test table structures (i.e., correct size, includes necessary fields, etc.) -- modify as necessary. [Top]

Two methods for normalizing data

There are two mechanisms for normalizing data. First, develop and refine the data list or entities. In most cases each entity needs a table of its own. Second, use general rules of thumb to determine when a table needs to be split. If identical data is being entered into two or more records the DB probably needs to be split. Every record should contain data specific to the item, person or event it represents. Avoid storing multiples of a particular item of information in a table. [Top]

07/15/00 MACurran & S. Kellum

Index